Microcircuit die-sawing protector and method

ABSTRACT

A method and apparatus for protecting hypersensitive microcircuits on the face of a semiconductor wafer from contamination and mechanical damage during die sawing and subsequent die handling operations include the provision of a plastic sheet having an array of protective domes formed into it, the array corresponding to the array of microcircuits on the wafer, and the temporary adhesion of the sheet to the face of the wafer such that each die in the wafer is covered by a respective one of the domes, with an associated one of the microcircuits protectively sealed therein. Die sawing is performed with the component side of the wafer facing up, the cut passing between the domes and through the thicknesses of both the domed sheet and the wafer such that each die is separated from the wafer, with a corresponding one other domes still attached to it. The domes may be removed later when the dies are located in a more benign environment by simply peeling them off the die. The invention enables the use of conventional die-handling equipment and results in improved device yield.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to microcircuit packaging in general, and inparticular, to a method and apparatus for protecting hypersensitivemicrocircuits on a semiconductor wafer from contamination and mechanicaldamage during die sawing and subsequent die-handling operations.

2. Description of the Related Art

Microcircuits are typically fabricated on the surface of a wafer of asemiconductor material, e.g., silicon, in a rectangular array ofidentical devices. The typical manufacturing process involves numerousmanufacturing steps, such as cleaning, printing, etching, doping,coating, plating, and ion implantation. Upon completion of these steps,and prior to the packaging of the individual microcircuits for use inelectronic devices, the microcircuits, together with an underlyingportion of the wafer, are separated from wafer into individual dies, or“chips.” This separation is typically accomplished by a mechanicalsawing operation, or by breaking the wafer along scribe lines created inthe wafer by a laser or a diamond-tipped scribe.

In conventional microcircuit die sawing practice, a layer of a stickytape, such as that sold by the Nitto Denko Corporation of Osaka, Japanunder the name “Nitto tape,” or that sold by the Lintec Company ofShiga, Japan, is attached to the backside of the wafer, which is thenplaced face up on the saw table, and sawn through down to, but notincluding, the tape backing. The individual dies are then removed fromthe tape by automated “pick-and-place” die-handling equipment thatincludes a needle that pierces the sticky tape from the underside tocontact the bottom surface of the die and separate it from the tape, andan arm that grasps the upper, circuit-containing surface of the diewith, e.g., a vacuum collect, and transports it to another location forsubsequent processing

Typical microcircuits manufactured in the above manner are substantiallyflat, i.e., the circuit components and elements are closely integratedwith each other, are substantially planar in form, and are typically onthe order of a few angstroms to a few microns thick. As such, they aremoderately resistant to contamination by dust particles and vaporsgenerated during the die-sawing operation, as well as to mechanicaldamage occasioned by handling of the dies during die sawing andsubsequent manufacturing operations. In some instances, this resistanceto contamination and/or mechanical damage can be enhanced by the vapordeposition of a protective layer of silicon dioxide or silicon nitrideon the face of the microcircuits prior to die separation.

However, there are at least two classes of microcircuit devices that arehighly sensitive to contamination by die-sawing byproducts and/or tomechanical damage occasioned by handling during manufacturing, namely,the so-called “optical sensor” and “micro-machine” devices. An exampleof the former would include the “micro-mechanical display logic andarray” of A. M. Hartstein, et al., (U.S. Pat. No. 4,229,732), whileexamples of the latter would include the “electrostatic motor” describedby R.T. Howe, et al. (U.S. Pat. No. 4,943,750), or the “machinestructures” made by the method of Sparks et al. (U.S. Pat. No.5,427,975).

These latter types of devices have in common that both types includehighly fragile micro-structures and/or specialized reflective surfacesthat either extend, or face, upward from the face of the die, and theymay also include microscopic openings into the underlying semiconductorsubstrate, such as might be found in an integrated circuit pressuretransducer. For obvious reasons, these structures are highly susceptibleto both contamination by the dust, cooling liquids, and/or vaporousby-products generated by die-sawing, as well as to the mechanical damagethat could result from, e.g., a slight, unintended gust of air or dropof water incident on the face of the wafer. Such contamination or damagecould result in an entire wafer of relatively expensive devices beingruined and scrapped.

Accordingly, special manufacturing procedures and equipment are neededto handle these hypersensitive types of devices. This is particularly soat the stage of their manufacture at which the micro-features are fullydefined on the face of the wafer or on the separated dies, such asduring the die-sawing operation, or during subsequent die-mountingprocedures. The prior art methods and apparatus for dealing with thesespecial types of microcircuits described below, while workable, havesome associated drawbacks that adversely effect their efficiency.

The prior art method for die-sawing these hypersensitive types ofmicrocircuits is described in some detail in U.S. Pat. No. 5,362,681 toC. M. Roberts, Jr., et al. The method includes inverting the wafer facedown on the saw table and sawing it from the back face of the wafer. Toprotect the microcircuit devices on the front face of the wafer, thewafer is attached to a spacer film, typically a Mylar tape, carried on astretcher frame. The film has a pattern of openings in it correspondingto the array of dies on the face of the wafer, and is adhered to thefront face of the wafer, rather than to its backside, as is done withconventional microcircuits. The spacer film is sized such that itsperiphery overhangs the margin of the wafer. Four sets of alignmentholes, oriented with respect to the “streets” between the dies, arepunched into the tape on opposite sides of the wafer outside of itsmargin. A second film is then adhered to the backside of the spacer filmto seal the component openings in the spacer film.

The wafer is then placed upside-down on the saw table, and aligned withrespect to the saw blade by means of an alignment system that aligns thewafer with respect to the above-described four sets of alignment holesin the spacer film. The wafer is sawed through its back side down to,but not through, the spacer film to singularize the dies from the wafer.The dies are then individually pushed and lifted from the spacer film bymeans of specially designed pick-and-place equipment that includes aspecial, hollow “needle cluster” that pushes upwardly through the spacerfilm to contact the edges of the die to separate it from the film, andan arm that grasps the die from the back side with a vacuum collet. Thearm then inverts the die 180 degrees such that its front face facesupward, then hands the die off to a second arm also equipped with aspecial hollow vacuum collet that enables the arm to grasp the sensitivefront side of the die without damaging the microcircuit thereon.

While the above prior art method is workable, it has several drawbacksassociated with it: First, since the wafer is sawn upside down, theunderside of the dies, rather than their top surfaces, are presented forremoval of the dies from the spacer film. This prevents the use ofconventional automated pick-and-place equipment, and necessitates theuse of the specially adapted pick-and-place apparatus described above toaccommodate the sensitive micro-structures located on the top side ofthe die. It would be desirable if conventional pick-and-place diehandling equipment could be used with these hypersensitive types ofchips.

Also, because removing the dies from the spacer film destroys the sealedenclosure that protects the microcircuits during the sawing operation,once the dies are removed from the spacer film, they must thereafter bemaintained in a clean room environment and are at increased risk ofmechanical damage and/or contamination until they have been individuallypackaged in a protective enclosure. It would therefore be desirable ifthe protection afforded the delicate microstructures during the sawingoperation could be retained with the individual dies after sawing sothat they could be safely handled and stored in a less criticalenvironment.

Further, because the wafer is sawn face down on the table, the scribelines on its face, and indeed, the microcircuits themselves, are notdirectly accessible for saw alignment purposes. Instead, the saw must beindirectly aligned with the wafer by means of the four sets of alignmentholes in the film spacer described above. Since there is a tolerancebuildup between the various parts, this results in a loss of precisionin the location of the saw cuts, and thus necessitates a wider spacing,or street, between devices to accommodate the tolerance buildup. Inparticular, the width of the scribe lines necessitated by this prior artmethod is 12 mils, i.e., four times as great as the conventional diespacing, or scribe line width, possible with a wafer that is sawn faceup. This translates into a waste of wafer space and a concomitantreduction in device-per-wafer yield.

What is needed, then, is an effective method and apparatus for handlingthese types of fragile and contamination-sensitive microcircuits thatovercomes the above problems in a simple, inexpensive, and efficientmanner.

SUMMARY OF THE INVENTION

According to this invention, a simple, inexpensive, and efficient methodand resulting structure are provided for protecting the microcircuits onthe face of a semiconductor wafer from contamination and damage duringwafer sawing and subsequent die attachment procedures. The methodcomprises forming a sealed, protective dome over each of themicrocircuits on the face of the wafer such that, when the individualmicrocircuits and associated dies are sawn from the wafer, theprotective dome over each of the microcircuits remains associated withand protectively sealed over its associated microcircuit.

In one embodiment of a saw protector, a first sheet of material isselected, preferably plastic, having an area sufficient to cover all ofthe microcircuits in the wafer. A pattern, or array, of protective domescorresponding to the array of microcircuits on the wafer is formed intothe sheet, e.g., by molding or thermo forming. Each of the domes isformed to have a height greater than the maximum height of any etched ormechanical feature extending upward from the microcircuits, and aperiphery at least as great as the periphery of its correspondingmicrocircuit.

The edges of the sheet are preferably trimmed such that, when the sheetoverlays the wafer, the ends of conventional saw-alignment scribe lineson the face of the wafer are exposed for use by either manual orautomated optical saw alignment equipment. The sheet is oriented withthe dome openings facing toward the wafer, and is aligned with respectto it such that each of the domes is disposed over a correspondingmicrocircuit. The sheet is then impermanently adhered to the face of thewafer, preferably by means of a pressure-sensitive adhesive having apeel-off protective backing previously applied to the sheet, such thateach microcircuit on the face of the wafer is individually covered byand protectively sealed within its own corresponding dome duringdie-sawing and subsequent die handling operations.

When the dies are thereafter separated from the wafer by sawing of thewafer, the wafer is sawn with its front side facing up, and the cut ismade to pass along the scribe lines between the dome-covered dies, andto cut through both the domed sheet and the wafer so that a portion ofthe sheet, including the protective dome over each microcircuit, remainsattached to and protectively sealed over its corresponding microcircuitand associated die.

In an alternative embodiment, the sheet is selected from a materialhaving a thickness greater than the maximum die-feature height, and thedomes are partially defined, e.g., by die-cutting, to comprise openingsthat extend through the entire thickness of the sheet. Thesethrough-openings facilitate alignment of the sheet with the wafer, asthe desired disposition of the microcircuits within the openings may bereadily visualized through the upper surface of the sheet during itsalignment with the wafer using automated optical pattern recognitionmethods. A second sheet having a periphery conforming to the first sheetis then adhered to the top surface of the first sheet to close off thethrough-openings and thereby form individual, sealed protective domesover each microcircuit. As with the first embodiment, the saw cut ismade from the front face, or top surface of the wafer, with the sawpassing along the scribe lines between the dies and through both sheetsof the saw protector, and then through the thickness of the wafer suchthat, when the dies are separated from the wafer, each is accompanied byits own sealed protective dome over the associated microcircuit. The diecan be picked up and handled by means of the domed enclosure, whichaccompanies the die and protects the microcircuit on it, both during thesawing operation and subsequently, e.g., during die attachment, yet theenclosure is easily removed at a later stage by simply peeling it awayfrom the chip.

A better understanding of the invention, along with its many attendantfeatures and advantages, may be had from a consideration of thefollowing detailed description of its preferred embodiments,particularly if reference is also made to the figures in theaccompanying drawings. Following is a brief description of thosedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a semiconductor wafer having an array of diesand associated microcircuit devices formed on its face;

FIG. 2 is a cross-sectional view through one of the dies and associatedmicro-circuits of the wafer shown in FIG. 1, as revealed by the crosssection taken along the lines II—II therein;

FIG. 3 is a plan view of the wafer illustrated in FIG. 1 showing a firstsheet of one embodiment of a saw protector in accordance with thepresent invention overlying the face and dies of the wafer;

FIG. 4 is a cross-sectional view through one of the dies and associatedmicrocircuits of the wafer shown in FIG. 3, as revealed by the crosssection taken along the lines IV—IV therein, showing a portion of thefirst sheet of the saw protector overlying the face of the die;

FIG. 5 is a plan view of the wafer and saw protector first sheetillustrated in FIG. 3 showing a second sheet of the saw protectoroverlying the first sheet and partially broken away to reveal the firstsheet;

FIG. 6 is a cross-sectional view through one of the dies and associatedmicrocircuits of the wafer shown in FIG. 5, as revealed by the crosssection taken along the lines VI—VI therein, showing a portion of thefirst and second sheets of the saw protector overlying the face of thedie and forming a protective dome over the associated microcircuitthereon;

FIG. 7 is an elevational cross-section through a pair of adjacent diesof the wafer and saw protector of FIG. 5 showing a saw kerf separatingthe dies and a dome portion of the saw protector of the presentinvention overlying the face and associated microcircuit of each die.

FIG. 8 is an elevational cross section through one of the dies and anassociated saw protector protective dome of the present invention,showing the die mounted to a substrate of a microcircuit package, withthe protective dome still in place.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a plan view of a conventional semiconductor wafer 1 of thetype concerned with here showing a number of microcircuits 2 (shown ascrosshatched circles), each formed on the top of a corresponding die 3.The dies, or “chips,” are typically square in shape, and are defined ina rectangular array on the face 4 of the wafer by a plurality of lines 5a, 5 b mechanically scribed on the face of the wafer. The wafers areusually round, are provided in a variety of diameters, and typicallyhave at least one segment removed at a margin of the wafer to define aflat edge 6, called a “primary flat.”

The primary flat 6 is oriented with respect to the underlyingcrystalline structure of the wafer 1, and the scribe lines 5 a, 5 b are,in turn, oriented with respect to the primary flat, to ensure that thearray of dies 3 is appropriately aligned with the break pattern of thewafer. In FIG. 1, one set of parallel scribe lines 5 a is shownintersecting the primary flat orthogonally, while a second set ofparallel scribe lines 5 b is shown parallel to the primary flat andorthogonal to the first set.

The number of microcircuits 2 that can be formed on a single wafer 1depends on the size of the wafer and the size of the individualmicrocircuits, and can range from a single microcircuit per wafer, toseveral hundred. When fabrication of the microcircuits is complete, andprior to their incorporation into individual packages for use inelectronic devices, the microcircuits must be separated from the wafer1. While this may be accomplished by simply breaking the wafer along thescribe lines 5 a, 5 b, it is more typically done today by means of amechanical sawing operation using a very thin, rotating blade coatedwith a diamond-abrasive to minimize silicon loss and maximize deviceyield. In the typical die-sawing operation, the scribe lines serveprimarily as saw alignment guides, and are typically 3 mils (0.003″)wide.

As discussed above, there are at least two classes of microcircuitdevices that are not amenable to conventional die-separation processesbecause they are particularly sensitive to contamination by die-sawingbyproducts and/or to mechanical damage occasioned by handling. These arethe so-called “optical sensor” and “micro-machine” devices describedabove, which are characterized by extremely fragile micro-structuresand/or critical reflective surfaces that face, or project, upward fromthe surface of the device, and hence, require special protection duringdie sawing and subsequent die handling to prevent their being damaged.

A first embodiment of a sawing protector 10 of the present inventionthat overcomes the problems of the prior art method of handling thesemore sensitive microcircuits is illustrated in plan view in FIGS. 3 and5. As shown in FIG. 3, the protector 10 comprises a first sheet 12 ofmaterial, preferably a transparent, semi-rigid plastic, that is easy tosaw, but which is not so soft that it binds or loads up the blade of thesaw. The first sheet 12 has an area sufficiently large to cover all ofthe dies 3 in the face 4 of the wafer 12, and a thickness greater thanthe maximum height of any microcircuit feature extending upward from theface of the dies, such as the cantilever beam mirrors of anelectrostatic light valve microcircuit. In this regard, it has beenfound that a material of from between about 1 to 5 mils in thickness isadequate for most purposes, and either of the conventional sticky tapessold by Nitto Denko Corp., product name/no. “SWT-10,” or the Lintec Co.,product name/no. “Adwill T-5782” have been found to be acceptable forthis purpose.

A pattern of openings 14 is then formed into the first sheet 12, thepattern corresponding to the array of microcircuits 2 on the face of thewafer 1. The openings are preferably round, as it has been found thatthis shape affords a better resistance to an undesirable deformation ofthe sheet caused, e.g., by sagging or pulling, than do rectangularopenings. The openings 14 extend through the entire thickness of thesheet, and each has a periphery, or circumference, that is at least asgreat as the periphery of its corresponding microcircuit device 2.

Importantly, the first sheet 12 is trimmed such that, when the openings14 in the sheet are aligned with the microcircuits 2 on the wafer 1, oneof the ends of each of the two sets of orthogonal scribe lines 5 a, 5 bon the face 4 of the wafer are exposed at one of the four edges 16, 18,20 and 22 of the sheet for saw alignment purposes.

The sheet 12 is then aligned with respect to the face of the wafer suchthat each of the microcircuits 2 is disposed within a correspondingthrough-opening 14. In the exemplary embodiment illustrated in FIG. 3,the through-openings 14 materially assist this alignment step, since theposition of the microcircuits within the openings is readily visualizedthrough the upper surface of the sheet. However, in an alternative,one-piece embodiment such as that described below, the openings 14 maybe closed off at the top, and it may therefore be desirable to providethe edges 16, 18, 20 and 22 of the sheet with a number of alignmentnotches 24 that are keyed to the scribe lines 5 a, 5 b for purposes of a“blind” alignment of the sheet 12 with respect to the wafer 1.

When the first sheet 12 is appropriately aligned with the wafer I suchthat each of the microcircuits 2 is disposed within a corresponding oneof the openings 14, the lower surface of the sheet is adhered to theface 4 of the wafer. For purposes of this adhesion, it is preferablethat the lower surface of the sheet be precoated with apressure-sensitive adhesive, one that does not adhere permanently to orleave a residue on a mounting surface when the sheet is peeled away fromit. The pressure sensitive adhesive provided on the lower surface ofconventional Nitto tape has been found to be satisfactory for thispurpose, and more desirably, comes with a peel-away protective backingon it that keeps the adhesive clean and fresh until it is ready for use.However, it is possible to avoid the use of a conventional adhesive onthe sheet altogether by using of a sheet of material comprising apartially polymerized plastic such that it is inherently sticky, or“tacky,” such as the above-identified tape sold by the Lintec Company,which relies on a UV-curable layer of acrylic as an adhesive means.

As shown in FIG. 3, when the first sheet 12 is adhered in place on thewafer 1, a second sheet 26 of material having an area sufficient tocover the first sheet is selected and trimmed so that its outlineconforms to the periphery of the first sheet, particularly at thetrimmed edges 16, 18, 20 and 22 of the latter, so that the ends of thesaw-alignment scribe lines 5 a, 5 b remain visible when the second sheetoverlays the first. The second sheet 26 is then aligned with and adheredto the upper surface of the first sheet 12 such that each of theopenings 14 is closed off at its top, thereby creating an individual,sealed protective enclosure, or dome 28, over each of the microcircuits2 and associated dies 3. Like the first sheet 13, the second sheet 26 ispreferably made of a semi-rigid plastic material, and Nitto tape or asimilar material, with a thickness of from about 1 to 5 mils, and asticky surface, such as a previously applied coating of apressure-sensitive adhesive, has been found to be a satisfactorymaterial for this component of the saw protector 10.

As seen in the plan view of FIG. 5, the wafer 1 and its array ofindividually sealed and protected microcircuits 2 are now ready fordie-sawing. Optionally, a layer of conventional sawing tape 34 (see FIG.7) may be applied to the backside of the wafer, as described above inconnection with conventional microcircuit die sawing, to hold the chipstogether in a matrix after the dies are sawn from the wafer. As withconventional, non-sensitive microcircuits, sawing is then accomplishedwith the top, or circuit surface, of the wafer face up on the saw table,using the visible ends of the scribe lines 5 a, 5 b for saw alignment,thereby enabling the same degree of sawing precision, and hence, deviceyields, heretofore achievable only with conventional microcircuit chips.The saw cut is made through the top surface of the wafer, with the bladepassing along the transverse scribe lines 5 a, 5 b between the dies 3,to cut through the thicknesses of the first and second sheets 12 and 26of the saw protector 10, and thence, through the face of the wafer 1such that, when the individual microcircuits 2 and associated dies 3 areseparated from the wafer, a portion 30 of the protector, including theprotective dome 28 covering each of the dies, remains associated withand protectively sealed over its corresponding microcircuit and die, asprogressively illustrated in FIGS. 2, 4, 6 and 7.

In FIG. 2, an individual microcircuit 2, a pair of adjacent wire bondpads 36, and their associated die 3 are shown separated from the parentwafer without a sawing protector 10 of the present invention in place onthe die to protect the microcircuit. In FIG. 4 the same die 3 is shownwith a portion of the first sheet 12 of the saw protector in place, themicrocircuit 2 being disposed within the through-opening 14 in the sheet12. FIG. 6 shows the same chip 3 with portions of both the first andsecond sheets 12 and 26 in place on the chip, and thus defining asealed, protective dome 28 over the microcircuit 2 on the face 4 of thedie 3.

FIG. 7 shows a pair of adjacent dies 3 attached at their bottom surfacesto a layer of conventional sawing tape 34, each microcircuit 2 havingits own, individual protective dome 28, as sawn from the parent waferand separated by the width of the saw kerf 32. Since the kerf does notextend though the bottom layer of conventional sawing tape 34, thelatter tape remains intact, and serves to hold the dies 3 together intheir relative positions after die sawing for handling convenience.

It may be seen that the dies 3 are thus amenable to handling byconventional pick-and-place die-handling equipment. In particular, thedies 3 are presented right-side-up, and can be safely picked up bygrasping the upper surface of the dome 28 without contacting the die 3itself. A conventional tape-separation needle can pierce the undersideof the tape layer 8 to contact the underside of an individual die 3 andseparate it from the tape 34 without fear of damaging the sensitivemicrocircuit 2 on the top surface of the die. Further, the die 3 can belifted off the tape 34 through the agency of the protective dome 28using a conventional vacuum collet on a conventional pick-and-place arm,again without concern for damaging the underlying sensitive microcircuit2. Hence, the need for a second arm, with a special collet on it forgrasping the sensitive upper surface 4 of the die 3 is eliminated, as isthe need to invert the die before attaching it to a substrate 38, suchas illustrated in FIG. 8.

The individual protective domes 28 may thus be left in place on the dies3 after sawing to continue protecting the underlying microcircuit 2until such time as direct access is needed to the microcircuit itself,such as at wire bonding to the die. Interim processing steps, such asdie attachment, can be carried out with the protective dome in place,which means that the die may be removed from a clean room environmentfor die attachment and still be protected from contamination andmechanical damage during such time. This is illustrated in FIG. 8,showing a die 3 attached to a semiconductor package substrate 38, bymeans of, e.g., a layer of adhesive 40. The substrate 38 may comprise,e.g., a lead frame or a printed circuit board, which typically wouldinclude a plurality of wire bond pads 42 on the substrate adjacent tothe die 3. The protective dome 28 may be left in place over themicrocircuit 2 during die attachment and until such time as directaccess to the top surface 4 of the die is required, e.g., at the wirebonding stage.

Those skilled in the art will recognize that a simplified embodiment ofthe saw protector 10 can be achieved by eliminating the second sheet 26and forming, e.g., by molding or thermo-forming, the pattern of closedprotective domes 28 directly into the first sheet 12 through its lowersurface. In this alternative embodiment, the thickness of the sheet 12can in fact be less than the maximum height of any microcircuit featureextending upward from the face 4 of the dies 3, provided that the domes28 have an internal height that is greater than such maximum die-featureheight, and, as in the case of the first embodiment, a periphery that isat least as great as the periphery of its underlying microcircuit 2. Theadvantage of this embodiment is that it eliminates the need for thesecond sheet 26 and the steps of trimming it and adhering it to theupper surface of the first sheet 12. Its disadvantage, relative to thefirst-described embodiment, is that, unless the sheet 12 is selected ofa very transparent or translucent material, the microcircuits 2 can nolonger be visualized through the openings 14 during alignment of thesheet 12 with the wafer, and accordingly, some provision, such as thealignment notches 24 described above, must be made to compensate forthat.

Indeed, those skilled in the art will by now recognize that, dependingon the particular problem at hand, other advantageous modifications andsubstitutions can be made to the method and apparatus of the presentinvention in terms of its materials, methods and practice, withoutdeparting from its scope. Accordingly, the particular embodimentsdescribed and illustrated herein should be understood as being exemplaryin nature, and not as limitations of that scope, which is defined by theclaims appended hereafter.

What is claimed is:
 1. A method for protecting an array of sensitivemicrocircuits on the front face of a semiconductor wager fromcontamination during sawing, comprising: forming a sealed, protectivedome over each of the microcircuits on the front face of the waferwithout contacting any portion of the respective microcircuits, whereinforming a sealed, protective dome over each of the microcircuitscomprises selecting a first sheet having upper and lower surfaces and anarea sufficient to cover all of the microcircuits on the wafer, forminga pattern of productive domes into the first sheet through the lowersurface thereof, the pattern corresponding to the array of microcircuitson the wafer, each of the domes having a height greater than the maximumheight of any microcircuit feature extending upward from the face of thewafer, and a periphery at least as great as the periphery of acorresponding one of the microcircuits, and adhering the lower surfaceof the first sheet to the face of the wafer such that each microcircuiton the wafer is individually covered by and protectively sealed within acorresponding one of the protective domes; trimming at least one edge ofthe first sheet such that, when the first sheet is adhered to the wafer,at least one end of at least one set of saw-alignment scribe line on theface of the wafer is exposed at that edge of the first sheet; and sawingthrough the wafer and between the domes from the front face of the waferto singulate the microcircuits, while leaving, the protective dome overeach microcircuit.
 2. The method of claim 1, further comprising applyingan adhesive to the lower surface of the first sheet.
 3. The method ofclaim 1, wherein trimming the at least one edge of the first sheetfurther comprises forming notches in the at least one edge that arealigned with corresponding ones of the scribe lines on the front face ofthe wafer when respective ones of the microcircuits on the wafer aredisposed below corresponding ones of the protective domes in the firstsheet.
 4. The method of claim 1, further comprising: grasping an uppersurface of a protective dome; and, picking the dome up with anassociated one of the microcircuits adhered thereto.
 5. The method ofclaim 1, wherein The first sheet is transparent.
 6. The method of claim1, wherein selecting the first sheet further comprises selecting a sheetwith a thickness greater than the maximum height of any microcircuitfeature extending upward from the face of the wafer, and forming theprotective domes further comprises forming openings through thethickness of the first sheet, and further comprising: selecting a secondsheet of material having an area sufficient to cover the first sheet;conforming the periphery of the second sheet to the periphery of thefirst sheet; and, adhering the second sheet to the first sheet such thateach of the openings is closed off, with a corresponding one of themicrocircuits being protectively sealed therein.
 7. The method of claim6, wherein the openings are circular in shape.
 8. The method of claim 6,wherein at least one of the first and second sheets is selected frommaterials having a pressure-sensitive adhesive with a peel-away backingon their lower surfaces.
 9. The method of claim 6, wherein at least oneof the first and second sheets is Nitto tape.
 10. The method of claim 6,further comprising: grasping an upper surface of a protective dome; and,picking the dome up with an associated one of the microcircuits adheredthereto.
 11. The method of claim 6, wherein each of the first and secondsheets is transparent.
 12. The method of claim 6, further comprisingadhering a back face of the wafer to a third sheet, and wherein sawingthough the wafer comprises sawing through the first sheet, the secondsheet and the wafer down to but not through the third sheet.
 13. Themethod of claim 12, wherein the third sheet comprises a wafer-sawingtape.
 14. The method of claim 12, further comprising: piercing the thirdsheet with a needle to contact a back side of a microcircuit with theneedle; and, pushing the microcircuit away from the third sheet with theneedle.
 15. A method of singulating a plurality of dies from asemiconductor wafer, the method comprising: providing a semiconductorwafer having an array of dies integral therein, the dies beingdelineated by two orthogonal sets of sawing lines defined on a frontface of the wafer; forming a protective dome over a central portion ofeach die in the wafer, each dome having a periphery sealed to the frontface of the wafer around a periphery of an associated one of the diestherein and a central region not contacting the front face of the die,while exposing at least a portion of the sawing lines on the front faceof the wafer; and, sawing between the domes and through the wafer fromthe front face thereof using the sawing lines as guides to singulate thedies from the wafer, with each die having an associated one of theprotective domes sealed thereon.
 16. In a semiconductor wafer having afront face with guide lines delineating an array of fragilemicrocircuits thereon, a method for singulating the microcircuits fromthe wafer without damaging them, the method comprising: providing asheet having a first surface; forming an array of protective domes inthe sheet through the first surface thereof, the array of domescorresponding to the array of microcircuits on the front face of thewafer; adhering the first surface of the sheet to the front face of thewafer without contacting any of the microcircuits with the sheet, andwith respective ones of the microcircuits being protectively sealedunder corresponding ones of the domes; forming means in the sheet forexposing at least a portion of each of the guide lines on the wafer;and, cutting through the sheet and the wafer from the front face thereofusing the exposed guide lines as cutting guides to singulate themicrocircuits from the wafer, and with corresponding ones of theprotective domes remaining protectively sealed over respective ones ofthe microcircuits after singulation thereof.
 17. A method of singulatinga plurality of semiconductor dies comprising: providing a semiconductorwafer having an array of the semiconductor dies therein, wherein eachsemiconductor die includes a central portion having a microcircuit at afront face of the wafer, and the semiconductor dies of the wafer aredelineated by two sets of orthogonal sawing lines on the front face ofthe wafer; step for sealing a peripheral portion of each of the dies ofthe wafer around the respective central portion and enclosing themicrocircuit thereof without contacting the microcircuit; step forexposing at least some of said sawing lines; and then sawing through thewafer from the front face of the wafer along the sawing lines whle therespective dies are sealed and the microcircuits are enclosed so as tosignulate the semiconductor dies.